USS Thresher (SSN-593) was the lead boat of her class of nuclear-powered attack submarines in the United States Navy. She was the U.S. Navy's second submarine to be named after the thresher shark.
On 10 April 1963, Thresher sank during deep-diving tests about east of Cape Cod, Massachusetts, killing all 129 crew and shipyard personnel aboard. Her loss was a watershed moment for the U.S. Navy, leading to the implementation of a rigorous submarine safety program known as SUBSAFE. The first nuclear submarine lost at sea, Thresher was also the third of four submarines lost with more than 100 people aboard, the others being the French Surcouf, sinking with 130 personnel in 1942, USS Argonaut, lost with 102 aboard in 1943, and Russian Kursk, which sank with 118 aboard in 2000.
Significance of design and loss
Created to find and destroy Soviet submarines, Thresher was the fastest and quietest submarine of its day, matching the smaller, contemporary . She also had the most advanced weapons system, including launchers for the U.S. Navy's newest anti-submarine missile, the SUBROC, as well as passive and active sonar that could detect vessels at unprecedented ranges. Shortly after her loss, the Commander of Submarine Force Atlantic wrote in the March 1964 issue of the U.S. Naval Institute's monthly journal Proceedings that "the Navy had depended upon this performance to the extent that it had asked for and received authority to build 14 of these ships, as well as an additional 11 submarines with very much the same characteristics. This was the first time since World War II that we had considered our design sufficiently advanced to embark upon construction of a large class of general-purpose attack submarines."
Following Navy tradition, this class of subs was originally named Thresher after the lead boat. When Thresher was struck from the Naval Vessel Register on 10 April 1963, the class name was changed to that of the second boat, . Having been lost at sea, Thresher was not decommissioned by the U.S. Navy and remains on "Eternal Patrol".
Early career
The contract to build Thresher was awarded to Portsmouth Naval Shipyard on 15 January 1958, and her keel was laid on 28 May 1958. She was launched bow first on 9 July 1960, was sponsored by Mary B. Warder (wife of World War II skipper Frederick B. Warder), and was commissioned on 3 August 1961, Commander Dean L. Axene commanding.
Thresher conducted lengthy sea trials in the western Atlantic and Caribbean Sea areas in 1961–1962. These tests allowed a thorough evaluation of her many new and complex technological features and weapons. She took part in Nuclear Submarine Exercise (NUSUBEX) 3–61 off the northeastern coast of the United States from 18–24 September 1961.
On 18 October 1961, Thresher headed south on a three-week test and training cruise to San Juan, Puerto Rico, in company with the diesel-electric submarine , arriving 2 November. Her reactor was shut down in accordance with standard procedure while in port. No shore power connection was available in San Juan, so the ship's backup diesel generator was used to carry the "hotel" electrical loads. Several hours later, the backup generator broke down and the electrical load was transferred to the ship's battery. Most of the battery power was needed to keep vital systems operating and to restart the reactor, so lighting and air conditioning were shut down. Without air conditioning, temperature and humidity in the submarine rose, reaching after about 10 hours. The crew attempted to repair the diesel generator (four men received Navy commendation medals for their work that night). It became apparent that the generator could not be fixed before the battery was depleted, so the crew tried to restart the reactor, but the remaining battery charge was insufficient. The captain returned to the ship from a shore function just after the battery ran down. The crew eventually borrowed cables from another ship in the harbor and connected them to the adjacent Cavalla, which started her diesels and provided enough power to allow Thresher to restart her reactor.Polmar, pages 13–17
Thresher conducted further trials and fired test torpedoes before returning to Portsmouth on 29 November 1961. The boat remained in port through the end of the year, and spent the first two months of 1962 with her sonar and SUBROC systems under evaluation. In March, she participated in NUSUBEX 2–62 (an exercise designed to improve the tactical capabilities of nuclear submarines) and in anti-submarine warfare training with Task Group ALPHA.
Off Charleston, South Carolina, Thresher undertook operations supporting development of the SUBROC anti-submarine missile. She returned briefly to New England waters, after which she proceeded to Florida for more SUBROC tests. While moored at Port Canaveral, Florida, the submarine was struck by a tug, which damaged one of her ballast tanks. Repairs were made at Groton, Connecticut, by the Electric Boat Company, and Thresher then went south for more tests and trials off Key West, Florida, before returning northward. The submarine entered Portsmouth Shipyard on 16 July 1962 to begin a scheduled six-month post-shakedown availability to examine systems and make repairs and corrections as necessary. The work took longer than expected, lasting nearly nine months. The ship was finally recertified and undocked on 8 April 1963."USS Thresher", article by Vice Admiral E.W. Grenfell, U.S. Naval Institute Proceedings, March 1964; accessed 6 April 2013.
Sinking On 9 April 1963, Thresher left Kittery, Maine, at 8 a.m. under command of Lieutenant Commander John Wesley Harvey. She met with the submarine rescue ship at 11 a.m. to begin her initial post-overhaul dive trials in an area east of Cape Cod, Massachusetts. That afternoon, Thresher conducted an initial trim-dive test, surfaced, and then performed a second dive to half of her 1,300-foot (400-meter) test depth. Thresher had been to her test depth about 40 times before entering the ship yard in late 1962. She remained submerged overnight and re-established underwater communications with Skylark at 6:30 a.m. on 10 April to commence deep-dive trials. Following standard practice, Thresher slowly dived deeper as she traveled in circles under Skylark to remain within communications distance, pausing every of depth to check the integrity of all systems. As Thresher neared her test depth, Skylark received garbled communications over underwater telephone indicating "minor difficulties, have positive up-angle, attempting to blow", and then a final, even more garbled message that included the number "900". Skylark received no further communication, and surface observers gradually realized that a problem had occurred.
By mid-afternoon, 15 Navy ships were en route to the search area. At 6:30 p.m., the commander of Submarine Force Atlantic sent word to Portsmouth Naval Shipyard to begin notifying the crew's family members, starting with Commander Harvey's wife Irene, that Thresher was missing.
Chief of Naval Operations Admiral George W. Anderson Jr. went before the press corps at the Pentagon to announce that the submarine was lost with all hands. President John F. Kennedy ordered all flags to be flown at half mast from 12 to 15 April in honor of the 129 lost submariners and shipyard personnel.
Search and recovery
By morning on 11 April, submarines USS Seawolf and USS Sea Owl, both operating near Thresher location, were ordered to join in the search for the missing submarine. The Navy quickly mounted an extensive search with surface ships and support from the Naval Research Laboratory (NRL), with its deep-search capability. The laboratory's small acoustic research vessel Rockville, with a unique trainable search sonar, left on 12 April 1963 for the search area. Rockville was to be followed by other personnel with a deep-camera system. , , and became engaged in a close sonar search of an area square. , , and investigated likely contacts found in the sonar search. The NRL deep-towed camera system and personnel later operated from James M. Gilliss with some success, finding debris later confirmed to be from Thresher. The bathyscaphe Trieste was alerted on 11 April and brought from San Diego to Boston. It was deployed for two series of dives into the debris field; the first taking place from 24 to 30 June, and the second from late August until early September. The equipment-handling capability of Gilliss proved inadequate, even hazardous, to handle the towed vehicle, and the entire search was paused in September.
The inadequacy of the existing small Auxiliary General Oceanographic Research (AGOR) vessels such as James M. Gilliss for handling deep-towed search vehicles led to a search for a vessel of a size and configuration that could handle such equipment in a sheltered area. In late 1963, that search resulted in the acquisition of , with the intent to eventually add a sheltered center well for deploying equipment.
The 1964 search included Mizar (with partial modifications but not a center well), , and Trieste II, Trieste successor. That submersible incorporated parts of the original bathyscaphe and was completed in early 1964. The bathyscaphe was placed on board and shipped to Boston. Mizar did have a system called Underwater Tracking Equipment (UTE) by which it could track its towed vehicle, and it was planned for use to track Trieste. Before her departure from NRL in Washington, Mizar was equipped with highly sensitive proton magnetometers furnished by the instrument division of Varian Associates in Palo Alto. In use, the magnetometers were suspended on an electrical line that also towed underwater video cameras.
Mizar sailed on 25 June to begin the deep search and found the wreck within two days. The shattered remains of Thresher hull were on the sea floor, about below the surface, in five major sections. Most of the debris had spread over an area of about . Major sections of Thresher, including the sail, sonar dome, bow section, engineering spaces section, operations spaces section, and the stern planes were found. By 22 July, most of the lost submarine had been photographed. In early August, the entire task force returned to the area with the submersible. Its first two dives were unsuccessful, but on the third dive, the UTE enabled placement of Trieste II on the wreck, at first not seeing wreckage because the bathyscaphe was sitting upon it.
Trieste II was commanded by Lieutenant John B. Mooney Jr., with co-pilot Lieutenant John H. Howland and Captain Frank Andrews, in an operation that recovered parts of the wreckage in September 1964.
On 9 July 2021, the United States Navy declassified the narrative of the submarine Seawolf during the search for Thresher. Seawolf detected acoustic signals at 23.5 kHz and 3.5 kHz as well as metal banging noises which were interpreted at the time as originating from Thresher. However, after the commander of Task Group 89.7 ordered that echo ranging and fathometers be secured so as to not interfere with the search, no further acoustic signals were detected by Seawolf other than those originating from other searching ships and the submarine Sea Owl. Ultimately, the Court of Inquiry determined:
Cause